The invention specifically applies to the independent brake line of a locomotive, for example, to the 20 Line in the EPIC.sup.a 3102 Braking system.
The independent brake system of a locomotive operates independently of the automatic airbrake system which includes the brake air line which is connected between all the railway cars in a train. The independent brake system applies brakes only on the locomotive. It is used, for example, when a locomotive is not connected to other railway cars, but is moved independently, for example, within a switchyard or a maintenance facility.
The independent brake system of a locomotive has a brake air line which is pressurized to apply brakes on the locomotive and is depressurized to release brakes. The independent brake system works in a manner exactly opposite to the automatic airbrake system of a train, in which the brake line is pressurized to remove brakes and depressurized to apply brakes.
In addition to its use for controlling an isolated locomotive in a switchyard or maintenance facility, the independent brake system is also used on other occasions when it is desired to apply brakes in the locomotive, but not in the other railway cars. For example, it is generally desirable for an engineer to place all the cars in a train in either a tension mode, or in a compression mode to reduce impact forces on couplers and draft gears due to relative motion of coupled cars. To place a train in a compression mode, as for example, prior to descending a grade, an engineer may retard the locomotive using the independent brake system so that the line of cars compresses against the locomotive.
The EPIC.sup.a 3102 Braking system uses transducers to measure the pressure in the independent application and release line. Difficulty has been experienced during winter weather conditions due to freezing of moisture in the independent application and release line. The transducers which measure pressure in the independent application and release line may freeze, or the fluid pathways to the transducers may become blocked with ice. Accordingly, it is necessary to remove condensed moisture from the independent application and release line. The independent application and release line may also have other fluid contaminants such as oil droplets and it is also desirable to purge these from the system.